1. Field of the Invention
The invention relates to a spindle structure, an electric motor, and a machine tool in which a through hole for allowing a fluid to flow is formed.
2. Description of the Related Art
Spindle structures and electric motors including a rotor in which a through hole for allowing a fluid, such as a refrigerant, to flow is formed are known (for example, Japanese Laid-open Patent Publication No. H6-170690 and Japanese Laid-open Patent Publication No. H10-146021).
In such devices, techniques for accelerating the flow of the fluid in the through hole of the rotor have been sought.